The present invention relates generally to methods of making nonwoven fabrics, and more particularly to a method of manufacturing a nonwoven fabric exhibiting improved physical characteristics while retaining aesthetic appeal, permitting use of the fabric in a wide variety of consumer applications.
The production of conventional textile fabrics is known to be a complex, multi-step process. The production of fabrics from staple fibers begins with the carding process where the fibers are opened and aligned into a feed stock known as sliver. Several strands of sliver are then drawn multiple times on drawing frames to further align the fibers, blend, improve uniformity as well as reduce the diameter of the sliver. The drawn sliver is then fed into a roving frame to produce roving by further reducing its diameter as well as imparting a slight false twist. The roving is then fed into the spinning frame where it is spun into yarn. The yarns are next placed onto a winder where they are transferred into larger packages. The yarn is then ready to be used to create a fabric.
For a woven fabric, the yarns are designated for specific use as warp or fill yarns. The fill yarn packages (which run in the cross direction and are known as picks) are taken straight to the loom for weaving. The warp yarns (which run on in the machine direction and are known as ends) must be further processed. The packages of warp yarns are used to build a warp beam. Here the packages are placed onto a warper which feeds multiple yarn ends onto the beam in a parallel array. The warp beam yarns are then run through a slasher where a water soluble sizing is applied to the yarns to stiffen them and improve abrasion resistance during the remainder of the weaving process. The yarns are wound onto a loom beam as they exit the slasher, which is then mounted onto the back of the loom. Here the warp and fill yarns are interwoven in a complex process to produce yardages of cloth.
In contrast, the production of nonwoven fabrics from staple fibers is known to be more efficient than traditional textile processes as the fabrics are produced directly from the carding process.
Nonwoven fabrics are suitable for use in a wide-variety of applications where the efficiency with which the fabrics can be manufactured provides a significant economic advantage for these fabrics versus traditional textiles. However, nonwoven fabrics have commonly been disadvantaged when fabric properties are compared, particularly in terms of surface abrasion, pilling and durability in multiple-use applications. Hydroentangled fabrics have been developed with improved properties, which are a result of the entanglement of the fibers or filaments in the fabric providing improved fabric integrity. Subsequent to entanglement, fabric durability can be further enhanced by the application of binder compositions and/or by thermal stabilization of the entangled fibrous matrix. However, the use of such means to obtain fabric durability come at the cost of a stiffer and less appealing fabric.
U.S. Pat. No. 3,485,706, to Evans, hereby incorporated by reference, discloses processes for effecting hydroentanglement of nonwoven fabrics. More recently, hydroentanglement techniques have been developed which impart images or patterns to the entangled fabric by effecting hydroentanglement on three-dimensional image transfer devices. Such three-dimensional image transfer devices are disclosed in U.S. Pat. No. 5,098,764, hereby incorporated by reference, with the use of such image transfer devices being desirable for providing a fabric with enhanced physical properties as well as an aesthetically pleasing appearance.
Heretofore, attempts have been made to develop nonwoven fabrics exhibiting the necessary aesthetic and physical properties. U.S. Pat. No. 5,393,304, discloses a washable spunlaced nonwoven cloth, with this patent contemplating use of a PAE binder composition (polyamide-amine-epichorohydrin) with inclusion of cotton fiber in the fibrous matrix.
U.S. Pat. No. 3,988,343, discloses a nylon fabric treated with a mixture of acrylic polymer and latex binder with tinting pigments. U.S. Pat. No. 5,874,159 contemplates providing a spunlaced fabric structure with durability by the provision of a bonding material in the form of a thermal plastic polymer, which may be provided in the form of a net, an apertured or punctured film, or molten drop form. The bonding material acts to join layers or laminations from which the fabric is formed.
For specific applications, a nonwoven fabric must exhibit a combination of specific physical characteristics. As an example, fabrics used in apparel should be soft and drapeable, yet withstand home laundering, and be resistant to abrasion (which can result in aesthetically displeasing fabric xe2x80x9cpillsxe2x80x9d). Fabrics used in the fabrication of apparel must also exhibit sufficient strength, tear resistance, and colorfastness to ensure a reasonable life span for the end-use article. The physical performance of a fabric in terms of liquid handling, i.e. perspiration control, is of utmost concern when apparel fabricated from such fabric is to be worn for extended lengths of time. These are among the characteristics which have been identified as being desirable for apparel applications including outerwear, workwear, footwear, and the like.
U.S. Pat. No. 5,478,635, discloses a knitted nylon fabric, necessary for abrasion resistance, being adhesively affixed to a nylon nonwoven fabric xe2x80x9creservoirxe2x80x9d. The construction of this laminate structure requires the knitting of nylon yarn followed by the application of polyurethane adhesive dissolved in a highly volatile solvent such as methylene chloride. U.S. Pat. No. 4,941,884 is directed to a method of fabricating an abrasion resistant woven material having good aesthetics.
Notwithstanding various attempts in the prior art to develop a nonwoven fabric acceptable for apparel use applications, a need continues to exist for a nonwoven fabric exhibiting aesthetic appeal while obtaining requisite mechanical characteristics.
In accordance with the present invention, a method of making a nonwoven fabric embodying the present invention includes the steps of providing a precursor web comprising a fibrous matrix. While use of staple length fibers is typical, the fibrous matrix may comprise substantially continuous filaments and combinations thereof. In a particularly preferred form, the fibrous matrix is carded and cross-lapped to form a precursor web. It is also preferred that the precursor web be subjected to pre-entangling on a foraminous forming surface prior to imaging and patterning.
The present method further contemplates the provision of a three-dimensional image transfer device having a movable imaging surface. In a typical configuration, the image transfer device may comprise a drum-like apparatus that is rotatable with respect to one or more hydroentangling manifolds.
The precursor web is advanced onto the imaging surface of the image transfer device so that the web moves together with the imaging surface. Hydroentanglement of the precursor web is effected to form an imaged and patterned fabric.
Subsequent to hydroentanglement, the imaged and patterned fabric may be subjected to one or more variety of post-entanglement treatments. Such treatments include application of a pre-dyeing finish, dyeing of the fabric by conventional textile dyeing methods, and optionally, a subsequent post-dyeing finish.
A further aspect of the present invention is directed to a method of forming a durable nonwoven fabric which exhibits an enhanced degree of softness and drapeability, while providing the necessary high resistance to tearing and abrasion, to facilitate use in a wide variety of applications. The fabric exhibits a high degree of absorbency, thus permitting its use in apparel applications in which the fabric can quickly and effectively remove moisture, thus improving wearer comfort.
A method of making the present durable nonwoven fabric comprises the steps of providing a precursor web that is subjected to hydroentangling. Polyester precursor webs, in either homogeneous form or formed as a blend with other polymeric and/or natural fibers, have been found to desirably yield soft hand and good fabric drapeability. The precursor web is formed into an imaged and patterned nonwoven fabric by hydroentanglement on a three-dimensional image transfer device. The image transfer device defines three-dimensional elements against which the precursor web is forced during hydroentangling, whereby the fibrous constituents of the web are imaged and patterned by movement into regions between the three-dimensional elements of the transfer device.
In the preferred form, the precursor web is hydroentangled on a foraminous surface prior to hydroentangling on the image transfer device. This pre-entangling of the precursor web acts to partially integrate the fibrous components of the web, but does not impart imaging and patterning as can be achieved through the use of the three-dimensional image transfer device.
Subsequent to hydroentangling, the imaged and patterned nonwoven fabric is treated with a pre-dye finish to lend further integrity to the fabric structure. The polymeric binder composition is selected to enhance durability characteristics of the fabric, while maintaining the desired softness and drapeability of the patterned and imaged fabric.
Other features and advantages of the present invention will become readily apparent from the following detailed description, the accompanying drawings, and the appended claims.